Activated carbon air filter

ABSTRACT

Disclosed is an air filter and a method of manufacture for an air filter which is much more cost effective and provides greater operational effectiveness than state-of-the-art air filters. The air filter includes an outer metallic shell which may be used to attach the filter in line to ducting of a heating, ventilation, and air conditioning (HVAC) system. The filter may further include a filter unit made of activated carbon material. The filter unit may have one or more sections and may have a honeycomb cross section.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND 1. Field

The present invention relates to an air filter for heating, ventilation,and air conditioning (HVAC) systems, and more specifically, an in lineactivated carbon air filter for HVAC system.

2. Background

In the state of the art, activated carbon HVAC filters pass air througha packed layer of granulated activated carbon. Naturally, the air flowtakes the path of least resistance through the granulated carbon. Thismeans that a typical filter will only use only a portion of the carbonbefore the filter no longer provides filtering effects. Because the airflow follows the path of least resistance, it will continue to flowwhere the activated carbon has absorbed all it can absorb. More likely,if not closely monitored, the inundated carbon will become even lessresistive to the air flow. Thus, a certain portion of the carbon filtermaterial never receives any airflow, and the filter material in thisportion of the filter is wasted. Because of the granulated and,therefore, inherently non-uniform nature of the material, there is noway to guarantee an evenly-distributed flow of air over the activecarbon filter material.

To better understand the air flow through a state-of-the-art filter, thestructure of such a filter will now be described in reference to FIG. 1.The state-of-the-art filters 100 are generally cylindrically shaped. TheHVAC filters include a metal, typically aluminum, frame 102 including aninterior cylindrical mesh wall 104 and an exterior cylindrical mesh wall106 spaced apart from one another, the inner wall having a smallerdiameter than the outer wall, and the gap filled with granulatedactivated carbon. At a first end 108, a first cap attaches to the outerwall 106 and the inner wall 104, the first cap 107 further including afirst solid portion located between a first end of the outer wall 106and a first end of the inner wall 104. This first solid portion preventsany of the granulated active carbon material from escaping the spacebetween the outer and inner walls 106, 104. The filter 100 furtherincludes a second cap 110 which it attached to a second end of the outerwall 106 and a second end of the inner wall 104. The second cap 110 hasa second solid portion 112 similar to the first solid portion. Thesecond solid portion 112 is located between the outer wall 106 and theinner wall 104. Again, this second solid portion prevents any granulatedactive carbon filter material from escaping from the space between theouter wall and the inner wall. The second cap further includes acylindrical flange 114 which extends from the filter parallel to thelongitudinal axis. An exterior side of the inner wall defines aninterior void in the filter.

Air may pass from adjacent to an exterior surface of the filter 100through a portion of the granulated active carbon material. Afterpassing through the granulated carbon material, the air may exit to theinterior void. Alternatively, depending on the design of the intake, theair may pass from the interior void through the perforated metalhousing, through the granulated active carbon filtering material, andthen out through the mesh of the outer wall. This air flow path reversesthat of the previous path.

This design inherently has a number of problems. The filter 100 is aconsumable item. Ideally, it would be very low cost. However, thestate-of-the-art filter includes several aspects which increase thecosts. First, the frame itself includes several aspects which increasethe cost. The mesh outer wall and inner wall are created from solidsheets which are punched to create the mesh. This uses the same amountof material as a solid sheet and adds labor. The sheet starts as asheet, and must have the unwanted material removed to create the mesh orperforation. Then, the sheet must be formed into the generallycylindrical shape. The caps must also be formed and attached to theouter wall and inner wall. Most critically, the second cap has a flangethat must be formed. Forming the flange is an expensive process whichsignificantly increases the cost. The second cap alone may be as much as30 to 40% of the cost of the filter.

Further, the process to add the active carbon is very labor intensive.Because the active carbon is granulated, the active carbon must becompacted to remove air gaps. If the compaction process does not providesufficient compaction, and air can pass around and not through theactivated carbon, no filtering take place. Thus, the granulated carbonmust be added to the space between the outer wall 106, inner wall 104,and first cap 107 in stages. After the granulated activated carbon isfirst added, the entire filter 100 must be vibrated so that thegranulated active carbon is compacted. After compaction, the granulatedactive carbon no longer occupies the entire volume of the space betweenthe outer wall 106, inner wall 104, and first cap 107. The process ofvibration and compaction must again be repeated for this next portion ofgranulated active carbon which is added. The process may have to berepeated several more times until there is no further compaction throughvibration.

Because the compaction process causes the granulated particles to grindagainst one another, a great amount of carbon dust is produced duringthe process. This carbon dust continues to be produced every time thefilter 100 is handled until the filter 100 is installed in the system.Once the filter 100 is installed, the dust may enter the HVAC system.This dust may be distributed undesirably throughout the HVAC system, andmay be sent out through the vent in to the environment of the structure.The carbon dust is not fit for respiration.

For the foregoing reasons, there is a need for an active carbon airfilter which has a lower cost of manufacture and does not emit carbondust both in the manufacturing process and in use.

BRIEF SUMMARY

Disclosed is an air filter for filtering contaminants from a heating,ventilation, and cooling system. The air filter may include a shell. Theshell may include one or more beads for strengthening the shell. Theshell may form a solid exterior wall. The solid exterior wall may definean interior. The air filter may further include one or more o-rings. Theone or more o-rings may be located in the one or more beads. The airfilter may also include a honeycomb carbon filter unit made of anactivated carbon material. The honeycomb carbon filter unit may belocated in the interior of the shell. The honeycomb carbon filter unitmay be adjacent to the one or more o-rings. The honeycomb carbon filterunit may have a wall. The wall may define an exterior surface and aninterior. The honeycomb carbon filter unit may further include ahoneycomb structure cross section in the interior.

Further disclosed is a method for manufacturing an air filter. Themethod may include forming a honeycomb carbon filter unit. The honeycombcarbon filter unit may be formed from activated carbon. The honeycombcarbon filter unit may include an exterior surface and a honeycomb crosssection. The honeycomb cross section may include a plurality ofchannels. The plurality of channels may extend an entire length of thehoneycomb carbon filter unit. The honeycomb carbon filter may include ahoneycomb carbon filter unit first end and a honeycomb carbon filterunit second end. The method may include strengthening the exteriorsurface with a compound or structure. The method may further includeattaching a shell to the exterior surface. The shell may include one ormore beads or cross bends. The honeycomb carbon filter unit may includea first structure on the first end and a second structure the secondend. The first structure on the first end and the second structure thesecond end which may cause air passing through the filter unit to movein a pre-determined pattern.

Further disclosed is an air filter for filtering contaminants from aheating, ventilation, and cooling system. The air filter may include afirst filter unit section. The first filter unit section may be of anactivated carbon material. The first filter section may include one ormore first exterior wall sections. The first filter section may alsoinclude a first essentially planar wall section. The first essentiallyplanar wall section may have a first essentially planar exterior surfaceextending between a first edge and a second edge of the one or moreexterior wall sections. The first essentially planar wall section mayalso have a first essentially planar exterior surface. The first filterunit section may have a honeycomb structure cross section. The airfilter may also have a second filter unit section. The second filterunit section may be made of an activated carbon material. The secondfilter section may include one or more second exterior wall sections.The second filter section may further include a second essentiallyplanar section. The second essentially planar section may have a secondessentially planar exterior surface. The second essentially planarsection may further include a honeycomb cross section. The secondessentially planar exterior surface of the second filter unit sectionmay be attached to the first essentially planar exterior surface of thefirst filter unit section so that the first filter unit section andsecond filter unit section are mirrored and form a combined filter unithaving a first end and a second end. The air filter may further includea metallic shell around and adjacent to the first arcuate wall portionand the second arcuate wall portion of the combined filter unit.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 shows a prior art air filter;

FIG. 2 shows a perspective cross section view of one embodiment of afilter unit;

FIG. 3 shows a plan cross section view of a second embodiment of filterunit in a completed filter;

FIG. 4 shows a perspective view of a third embodiment of a filter unit;and

FIG. 5 shows a perspective view of a fourth embodiment of a filter unit.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of an activated carbon air filter for use in a heating,ventilation, and air conditioning (HVAC) system, and is not intended torepresent the only form in which it can be developed or utilized. Thedescription sets forth the functions for developing and operating thesystem in connection with the illustrated embodiments. It is to beunderstood, however, that the same or equivalent functions may beaccomplished by different embodiments that are also intended to beencompassed within the scope of the present disclosure. It is furtherunderstood that the use of relational terms such as first, second,distal, proximal, and the like are used solely to distinguish one fromanother entity without necessarily requiring or implying any actual suchrelationship or order between such entities.

The state-of-the-art air filter uses a metal frame filled withgranulated active carbon. There are numerous issues inherent in such adesign. Critically, the issues cannot be mitigated by differingmanufacturing techniques. Rather, a redesign is required. The disclosedfilter reorients the air flow of the state-of-the-art filter by 90degrees. Rather than having an air path that passes air from outside toinside the filter, which is a path perpendicular to the air flow in theducting, the disclosed filter performs the filtration with an in-lineair flow. This flow provides better air handling, and increased ease ofinstallation and maintenance.

With reference to FIG. 3, the filter 10 may include an outer shell 12and a honeycomb carbon filter unit 14 located inside the shell 12. Theshell 12 may be formed from a single piece of material. The material maybe a galvanized sheet metal, a non-galvanized sheet metal, a vinyl, or apolymer.

With reference to FIG. 2, in one embodiment, the honeycomb carbonhoneycomb carbon filter unit 14 may have a generally cylindrical shape.Alternatively, the honeycomb carbon filter unit may have a prism shape,a parallelepiped shape, or any general shape which may accommodate ahoneycomb interior. The exemplary embodiment shown in FIG. 2 is notmeant to be limiting. The activated carbon may be formed into a solidshape through heat and compression, either by molding or by extrusion.Alternatively, compression alone may be used. In addition, in anyembodiment, a binding agent may be added to the activated carbon to addfurther structural integrity to the honeycomb carbon filter unit 14. Theheat may activate the binding agent, or the binding agent may beactivated by pressure alone. The honeycomb carbon filter unit 14 mayhave a solid wall 16 around a perimeter of the honeycomb carbon filterunit 14. When the honeycomb carbon filter unit 14 is generallycylindrical, the solid wall 16 may be cylindrical as well. When thehoneycomb carbon filter unit 14 is another shape, the solid wall maytake the shape of an exterior surface of the general shape. The solidwall 16 may have an inner surface 18 and an outer surface 20. Both theinner surface 18 and the outer surface 20 may extend from a first end 22of the honeycomb carbon filter unit 14 to a second end 24 of thehoneycomb carbon filter unit 14, the distance between the first end 22and the second end 24 defines a length of the honeycomb carbon filterunit 14. The outer surface 20 defines an outer circumference of thehoneycomb carbon filter unit 14. The inner surface 18 defines aninterior circumference of the honeycomb carbon filter unit 14.

The honeycomb carbon filter unit 14 may have an interior volume. Theinterior volume may be defined by the inner diameter and the length. Thehoneycomb carbon filter unit 14 may include a honeycomb cross section 26located in the interior volume. The honeycomb cross section 26 mayinclude one or more vertical dividers 28 and one or more horizontaldividers 30. The vertical dividers 28 and the horizontal dividers 30 mayeach have a first end which starts at a location on the inner surfaceand extends to a location opposite the first end on the inner surface18, each of the one or more vertical dividers 28 and each of the one ormore horizontal divers 30 defining a chord on the inner circumference.All of the vertical dividers 28 may be substantially parallel to oneanother. All of the horizontal dividers 30 may be substantially parallelto one another. Each of the vertical dividers 28 may be substantiallyperpendicular to each of the horizontal dividers 30, and vice versa. Thevertical dividers 28 may or may not be oriented vertically when thefilter 10 is installed. Moreover, the horizontal divers 28 may or maynot be oriented horizontally when the filter 10 is installed. The terms“vertical” and “horizontal” are merely to orient the structure of thefilter 10 for understanding of the disclosure and are not meant to belimiting.

Each of the vertical dividers 28 and the horizontal dividers 30 mayextend between the first end 22 of the honeycomb carbon filter unit 14and the second end 24 of the honeycomb carbon filter unit 14, thushaving a length substantially equivalent to that of the honeycomb carbonfilter unit 14. The combination of the one or more vertical dividers 28and one or more horizontal dividers 30 may define a plurality of throughchannels 32. The channels 32 may have a square cross section, or a roundcross section, or an oval cross section, or any shape which allows forthe passage of air, and depending on the form of the mold in which thehoneycomb carbon filter unit 14 is formed. The manufacturing process ofthe honeycomb carbon filter unit 14 is discussed in detail below.

Alternatively, the filter unit may not have dividers that define chords.Rather, the channels may be, for example, hexagons, the sides of whichare angled relative to one another. Because of this, no single dividerextending in a straight line is present. Instead, the divider portionsaround and between the channels may include portions angling indifferent directions. A similar structure may be accomplished usingoctagon shaped channels. Thus, the dividers in such embodiments areshared walls which define the hexagon or octagon shapes. Shapes otherthan hexagons and octagons are also contemplated. Any honeycomb patternmay be combined with any general exterior shape.

The honeycomb carbon filter unit 14 may be formed using a mold. Theprocess may start by obtaining the carbon in a powder form.Alternatively, the carbon may be obtained in another form and workedinto a powder form. When the honeycomb carbon filter unit 14 has asubstantially cylindrical shape, the mold may have a substantiallycylindrical wall. It is understood that when the honeycomb carbon filterunit 14 has an alternative shape, the mold will include acorrespondingly shaped wall. The interior of the cylindrical wall mayhave a diameter equal to that of an outer diameter of the honeycombcarbon filter unit 14 to be formed by the mold. Thus, the mold may havea circular cross section. The cylindrical wall may further have a firstend, and an opposite, second end. The mold may have a length greaterthan that of the finished honeycomb carbon filter unit 14. An interiorsurface of the cylindrical wall may define an interior void of the moldinto which the activated carbon powder is placed to form the honeycombcarbon filter unit 14.

The interior void of the mold may have several mold rods extendingtherethrough. The second end of the mold may have a cap which closes thesecond end of the cylindrical wall. A number of mold rods may beattached to, and extend from, the cap. The rods may be attached to thecap at a second end of each of the mold rods. Each of the mold rods maybe attached by welding or adhesives or any method which will permanentlyattach each mold rod to the cap. Permanent attachment means that themold rods may only be removed by damaging the connection between themold rod and the cap, and consequently, causing damage to either themold rod, the cap, or both in damaging the connection. The mold rods mayshare a common cross section. For example, the mold rods may each have asquare cross section, a round cross section, an oval cross section, ahexagonal cross section, or an octagonal cross section, or any othercross section which will achieve the desired honeycomb pattern in theinterior void of the honeycomb carbon filter unit 14. The mold rods mayextend from the cap through the interior void to the first end of themold. Thus, the mold rods may have the same length as the mold itself.Alternatively, a portion of the mold rods may have a first crosssection, and another portion a second cross section. Still furtheralternatively, the mold rods may have more than two cross sections.

To manufacture the honeycomb carbon filter unit 14, the mold may befirst filled with activated carbon powder. The activated carbon powdermay include a binding agent already mixed in. Alternatively, a bindingagent may be added to the mold separately. After the addition of theactivated carbon and binding agent, if one is being used, a piston maybe placed the in the first end of the mold. The piston may be generallydisc shaped to correspond to an interior void of the mold. The pistonmay include a disc body including apertures to accommodate the moldrods, as the piston moves within the mold. The piston may further havelongitudinal extensions on a proximal end to allow the piston to extendinto the mold. The piston may have extensions or forms on the distal endto form structures on one end of the filter unit or filter section whichpredetermine the path of air into the honeycomb on the interior of afilter unit. Either by hand, or using machine power, the piston may beinserted in the mold to compress the granulated activated carbon. Thepiston may compress the granulated activated carbon to a specifieddensity. Heat may be added to the mold to aid in activating the bindingagent when a binding agent is used in addition to the activated carbon.

Both the mold and the piston may be shaped so that both the first endand the second end of the honeycomb carbon filter unit 14 may have somestructure which causes the air to move in a pre-determined pattern asthe air first enters the honeycomb carbon filter unit 14. Of course,once the air molecules come in contact with the honeycomb cross section,the air molecules will cease moving according to the pre-determinedpattern. The breaking of the pre-determined pattern is of no concern,however. This is because the structure which causes the air to move inthe predetermined pattern is included with the filter unit to ensurethat as much air as possible comes in contact with the honeycomb carbonfilter unit 14, as opposed to passing through without making contact.For example, the first and second ends of the filter unit may be moldedwith a structure 48 so that the air moves in a vortex pattern.

The mold may be designed to produce one section of a multi-sectionhoneycomb carbon filter unit 14. As shown in FIG. 3, in someembodiments, the section may be a portion of the length of the honeycombcarbon filter unit 14, but the entirety of the cross section. This typeof sections may be referred to as a series section, because the filterunit is assembled by attaching a plurality of these sections 34 a, 34 bin line or series. The section length may be one half of the overalllength of the honeycomb carbon filter unit 14. Section lengths of lessthan one half of the filter unit length are also contemplated. Aftereach of the sections 34 a, 34 b is formed, the sections may be assembledend to end to form the honeycomb carbon filter unit 14. In addition, anactivated carbon material 36 may be placed at the joints of thesections. The material 36 may be a hog hair mat cut to match the crosssection of the honeycomb carbon filter unit 14. The piston may include alip mold around the circumference which forms an area 38 a, 38 b in theinterior void into which the material 36 may be placed so that thematerial 36 is not overly compressed when the sections 34 a, 34 b andmaterial 36 are assembled, and so that the sections 34 a, 34 b may havesufficient surface available for attaching to one another. The ends ofthe sections 34 a, 34 b may be butted together and an adhesive appliedto the surfaces of the filter sections to attach the sections 34 a, 34b. When series filter sections are molded, the piston may be configuredto mold one end of the filter section to a shape which causes air, whenpassing through the shape, to move in a predetermined pattern. Thus,when two identical sections are assembled, they may be assembled so thatthe shape is present at both the first end and the second end of theassembled honeycomb carbon filter unit 14.

As shown in FIG. 4, in other embodiments, the mold may be designed toform sections 40 a, 40 b which are the full length of the honeycombcarbon filter unit 14, but are a portion of the cross section of thehoneycomb carbon filter unit 14. This type of filter section 40 a, 40 bmay be termed a parallel filter section. Parallel filter sections may beassembled side by side to form a complete filter unit. For example, themold may form a substantially semi-cylindrical filter unit section. Asshown in FIG. 4, when the semi-cylindrical sections 40 a, 40 b areformed in the mold, the sections may have one arcuate wall section 42 a,42 b, and one planar wall section 44 a, 44 b. The planar wall andarcuate wall sections may join at their respective edges along thelength of both portions. The joining of the walls forms asemi-cylindrical cross section. Of course, the two wall sections are notformed separately. Each of the sections is formed of a unitary piece ofmaterial. Further, in embodiments where the honeycomb carbon filter unit14 is formed in a single piece rather than at least two sections, thehoneycomb carbon filter unit 14 is also formed of a single, unitarypiece of material. Thus, when the molding process is complete, twosemi-cylinders may be assembled by attaching them along their lengthplanar wall section 44 a to planar wall section 44 b to form a completesubstantially cylindrical honeycomb carbon filter unit 14. The sections40 a, 40 b may be joined using an adhesive on each of the planar walls44 a, 44 b. Like other embodiments, the sections 40 a, 40 b may have ahoneycomb interior 46 a, 46 b formed the same way the other embodimentswere formed.

The honeycomb carbon filter unit 14 may also be manufactured using anextrusion process. The activated carbon material may be loaded into theextrusion devices, and either the shape of FIG. 2 or the shape of FIG. 4may be extruded. In the case of both the shapes of FIGS. 2 and 4, filterunits 14 or filter unit sections 40 a, 40 b respectively, may be cut tolength. The filter unit sections 40 a, 40 b may be assembled asdescribed above. The activated carbon material is forced through a diewhich forms the desired cross section. As discussed above, the extrudedfilter unit or filter unit section may then have a polymer materialapplied to the exterior surface. As also described above, the same maybe added to both the first end surface and the second end surface oncethe filter unit or filter unit section is cut to length.

As shown in FIG. 5, a filter unit embodiment similar to that of FIG. 2may also be used in a fourth embodiment. As shown in FIG. 5, a honeycombcarbon filter unit 502 similar to that of FIG. 2 may be a first section502 of another embodiment of honeycomb carbon filter unit. The firstsection 502 may be placed inside a second section 520 which acts as asleeve for the first section 502. This configuration may allow thefilter 500 to fit larger HVAC ducting. The fourth embodiment uses twoconcentric filter sections 502, 520 to form the honeycomb carbon filterunit 500. The first filter section 502 may be a honeycomb carbon filterunit similar to that of FIG. 2. That is, it may be an extruded or moldedsubstantially cylindrical filter unit with a honeycomb cross section.Alternatively, again similar to the honeycomb carbon filter unit 14 ofFIG. 2, the filter unit may be substantially prism shaped,parallelepiped shaped, or any other shape which will accommodate thehoneycomb structure cross section 504 in the interior. Although theexample of FIG. 5 uses cylinders, it is understood that any other shapeeither specified above or obvious to one of ordinary skill in the artcould be used as well. The solid wall 506 of the first filter sectionmay be shaped so that it has a taper from the first end 510 to thesecond end 508 in the range of 2 to 10 mm. That is, the first end 510may have a diameter 2 to 10 mm less than a diameter of the second end508 or vice versa. The second filter section 520 may be a sleeve for thefirst filter section 502. The second filter section 520 may also besubstantially cylindrical and may have an interior cylindrical surface512 and exterior cylindrical surface 514. The interior cylindricalsurface 512 may be concave, and define a cylindrical void 516, while theexterior cylindrical surface 514 may be convex. The cylindrical void 516may be sized and shaped so that the first filter section 502 may beplaced in the cylindrical void 516 and the exterior surface 518 of thefirst filter section 502 may form a friction fit with the interiorcylindrical surface 512. An adhesive may also be used to attach thefirst filter section 502 to the second filter section 520. The distancebetween the exterior cylindrical surface 514 and the interiorcylindrical surface 512 may be varied to fit corresponding HVAC ductingsizes. For example, if the largest diameter first filter section 502which an extrusion device may produce is 8 inches, and the ducting ofthe HVAC system is 12 inches, a second filter section 520 with adistance of slightly less than 4 inches between the exterior cylindricalsurface 514 and the interior cylindrical surface 512 may be formed. Forexample, the distance may be 3 13/16 inches. This will allow for theshell 12 (not shown) to be placed on the exterior surface 514 and forsome taper on the end portions in order to form a friction fit betweenthe shell and the HVAC ducting.

Once any sections of the filter are assembled, a thermoset polymercompound may be added to the exterior surface 20 of the honeycomb carbonfilter unit 14 to add structural integrity during handling and furtherassembly. The thermoset polymer may be, for example, an epoxy, polyesterresin, a vinylester, or a thermoplastic. The thermoset polymer may besprayed on to the exterior surface 20 of the honeycomb carbon filterunit 14. Alternatively, the thermoset polymer may be applied using a dipcoating, a brush, or the honeycomb carbon filter unit 14 may even berolled against an application head to apply the thermoset polymer. Thethermoset polymer may further contain an adhesive compound which makesattaching the honeycomb carbon filter unit 14 to the shell 12 easier bypreventing the honeycomb carbon filter unit 14 from moving relative tothe shell 12 during assembly. Alternatively, any liquified or solidmaterial may be added to the exterior surface 20 of the honeycomb carbonfilter unit 14 to add strength to the honeycomb carbon filter unit 14during handling of the honeycomb carbon filter unit 14 for assembly. Thethermoset polymer may also be added to the surface, which may also becalled a face, of the first end and the surface, which may also becalled a face, of the second end of the filter unit. Liquid compoundsare preferred because of their generally lower cost and less intensivelabor in assembly.

The thermoset polymer may also include one or more of various fibermaterials to add strength to the honeycomb carbon filter unit 14. Thefiber material may be mixed in with the thermoset polymer to aid in easeof application. The thermoset polymer may then be applied in apredetermined orientation. In certain orientations, the fiber materialadds as much strength as possible to the honeycomb carbon filter unit.Alternatively, the fiber material may be applied separately from thethermoset polymer. Still further alternatively, the fiber material maybe applied alone.

As another alternative, a heat shrink wrap may be applied to theexterior surface of the honeycomb carbon filter unit. Heat shrink tubingis commonly sold in various sizes. The heat shrink tubing may be placedaround the exterior surface of the honeycomb carbon filter unit and thenheat applied to the heat shrink tubing to form a skin around theexterior surface of the honeycomb carbon filter unit. The tubing willnot cover the faces of the honeycomb carbon filter unit. This isinherent in the shape of the tubing. Thus, the thermoset polymer may beapplied to the first end and the second end. Alternatively, a fibermaterial may be applied to the first end and second end of the honeycombcarbon filter unit. Still further alternatively, the first end and thesecond end of the honeycomb carbon filter unit may be left untreated.

The shell 12 and honeycomb carbon filter unit 14 may be assembled toform the finished filter 10. The shell 12 may be formed from a sheet ofmaterial commonly used for ducting cut to size for forming the shell 12.In addition to having sufficient length to cover the honeycomb carbonfilter unit 14, the sheet for forming into the shell may have additionallength. The additional length may account for some length lost in addingfeatures to the sheet in order to add greater strength to the shell 12.Alternatively, or in addition, the sheet to be formed in the shell mayhave additional length for forming a flange which may be used inattaching the filter 10 to the HVAC system ducting to which the filter10 is to be attached.

The sheet to be formed into the shell 12 may have some fabrication workdone to it before the shell 12 and honeycomb carbon filter unit 14 arejoined. For example, the sheet may have one or more cross breaks formedin the sheet. The sheet may be bent on a bending machine to form somecross breaks. Alternatively, the sheet may be rolled in certainlocations to form beads 50, 52 to add strength to the sheet and preventthe sheet from buckling under loads. The beads may be of more than onesize, and may have more than one shoulder configuration. Using eithermethod, or both methods in combination, the sheet may be strengthened bythe addition of cross breaks or beads, or both.

Forming beads 50, 52 in the sheet may have other uses beyondstrengthening the sheet. For example, in embodiments where there is noadhesive added to the liquid polymer coating on the exterior surface ofthe honeycomb carbon filter unit 14, a first bead 50 may be locatedadjacent to the first end of the honeycomb carbon filter unit 14, and asecond bead 52 may be located adjacent to a second end of the honeycombcarbon filter unit 14. An o-ring 54 a, 54 b may be placed in each of thebeads to lock the honeycomb carbon filter unit 14 within the shell.Thus, in addition to strengthening the shell 12, the bead 50, 52 mayserve as a channel for containing a device for holding the honeycombcarbon filter unit 14 in a predetermined location. The o-ring 54 a, 54 bmay be made of a rubber or polymer material. The o-ring may be solid orhollow. Alternatively, the o-rings and an adhesive may be used incombination to keep the honeycomb carbon filter unit 14 from movingrelative to the shell 12.

Additional beads 60 a-d may be formed in the shell 12. For example,beads 60 a-d may be formed along the portion of the shell 12 housing thehoneycomb carbon filter unit 14. These beads 60 a-d may also be used toposition o-rings 62 a-d. However, the o-rings 62 a-d in these beads mayperform a different function. In some embodiments, the shell 12 may beformed first, and then the shell 12 and the honeycomb carbon filter unit14 joined. When this method of assembly is used, the honeycomb carbonfilter unit 14 may not abut the shell 12 around the entire exteriorcircumference of the honeycomb carbon filter unit 14. O-rings 62 a-d maybe placed in the beads 60 a-d to serve one or more purposes. Forexample, the o-rings 62 a-d may provide a better fit between thehoneycomb carbon filter unit 14 and the shell 12. Additionally, theo-rings 62 a-d may be used to form a seal between the honeycomb carbonfilter unit 14 and the shell 12. The seal will prevent any air fromescaping the filter 10 between the honeycomb carbon filter unit 14 andthe shell 12. Although four addition o-rings and beads are shown in FIG.3, fewer than four beads and o-rings may be used.

The shell 12 may include additional length past the first end of thehoneycomb carbon filter unit 14, and past the second end of thehoneycomb carbon filter unit 14 for attaching the shell to otherducting. The end portions 56, 58 of the sheet to be formed in to theshell may be worked before the shell is formed. The working may includeforming a flange for connecting the filter to the ductwork of an HVACsystem. The working may include additional cross breaks or beads tostrengthen the flanges, as they are likely to be both axially loadingand loading perpendicular to the longitudinal axis of the honeycombcarbon filter unit 14. The latter loading may induce shear forces orforces that cause bending, while the axial loading may cause buckling inthe flange or the other portions of the shell. The cross breaks orbeading or the combination of cross breaks and beading strengthen theflange and may prevent the forces from being applied to other areas ofthe shell.

The flange may be further worked to form a series of alternating ridgesalong opposing end portions of the sheet. The end portions will form theflange when the sheet is rolled to form the shell 12, as is discussed infurther detail below. A series of alternating ridges may be formed alongthe opposing ends of the sheet. The formation of these alternatingridges may also be referred to as crimping. This working of the endportions, from the edge of the sheet or shell to some distance back fromthe edge effectively shortens the width of the end portions by causingthe same amount of material to travel a longer distance. Because thesame amount of material cannot cover the same amount of distance withoutbeing stretched thinner, the forming of the alternating ridges causesthe end portion to be shorter. Because of the formation of the ridges,the end portions will curve or arc across the width of the sheet. Whenthe sheet is rolled to form the shell 12, these end portions with have asmaller diameter than the remainder of the shell.

The shoulder configuration of the beads 50, 52 adjacent to the first endand second end of the honeycomb carbon filter unit 14 on the shell mayalso provide a function in fitting the filter 10 to an HVAC system'sducting. The beads 50, 52 may be formed with shallow shoulders in orderto provide a range of dimensions to obtain a friction fit. For example,a first type of HVAC ducting may be 250 mm, and a second type of HVACducting may be 10 inches, which is approximately 254 mm. The shallowshoulder of beads 50, 52 creates a gentle slope to the edge of the shell12. At the edge the diameter is less than 250 mm. The diameter graduallyincreases along a length of the shell. The increasing diameter allowsfor a friction fit of the filter 10 to a range of HVAC ducting sizes,including 250 mm and 10 inches or 254 mm.

Alternatively, if a bead is formed, the bead may be formed with ashorter length one side than the other in order to form an end portionof the length of the shell 12 with an unequal circumference as comparedto other portions of the length of the shell 12. For example, theopposing end portions of the shell 12 may have a diameter greater than amiddle portion of the length of the shell 12 as apportioned by theaddition of two beads across the sheet at a distance apart substantiallyequal to the length of the honeycomb carbon filter unit 14. The portionof the sheet between the two beads may be the middle portion, and theportions between a bead and an edge of the sheet may form a first endportion and a second end portion. When the shell 12 is formed with theopposing end portions having a greater circumference than the remainderof the shell 12, the opposing end portion may be connected to the HVACducting in a different manner than when the opposing end portions have asmaller circumference than the remainder of the shell 12.

To form the filter 10, the honeycomb carbon filter unit 14 may be placedon the sheet in a predetermined location. For example, if two beads 50,52 have been formed in the sheet to strengthen the sheet, andcorrespondingly, the shell 12, or to act as a retention groove for ano-ring 54 a, 54 b, or both, the honeycomb carbon filter unit 14 may beplaced between the beads 50, 52. The first bead 50 may be adjacent tothe first end of the honeycomb carbon filter unit 14, and the secondbead 52 may be adjacent to the second end of the honeycomb carbon filterunit 14. If an adhesive has been applied to the honeycomb carbon filterunit 14, then the honeycomb carbon filter unit 14 may be placed on agenerally flat sheet. The generally flat sheet may have some curvatureat the opposing end portions if the series of alternating ridges hasbeen formed there. Alternatively, the sheet may be curved so that thefilter settles to the apex of the curve. This configuration helps ensurethat the honeycomb carbon filter unit 14 does not move as the shell 12is formed. Alternatively, the adhesive may be applied to the sheet, andthe honeycomb carbon filter unit 14 placed on the sheet in the locationof at least some of the adhesive.

The sheet may then be rolled around the exterior surface of thehoneycomb carbon filter unit 14 to form the shell 12. After the rolling,the sheet may have material which extends beyond the first end and thesecond end of the honeycomb carbon filter unit 14. The sheet may alsohave material which is excess and would overlap as the sheet is rolledaround the exterior circumference of the honeycomb carbon filter unit14. This excess material may be used to form a closed seam. One edgeportion may be folded over the opposing edge, and then the entire excessfolded as flat as possible to the exterior surface of the shell 12.Forming such a seam prevents the shell 12 from unrolling.

If one or more series of alternating ridges were formed in the opposingend portions of the sheet, then the circumference of those end portionsmay be less than the interior circumference of the ducting to which thefilter 10 is to connect. Thus, the reduced circumference of the opposingend portions allows the opposing end portions of the filter 10 to beinserted in the interior of the ducting of an HVAC system, and willprovide a friction fit between the end portions and the ducting of theHVAC system. In addition, duct tape may be used to ensure the connectionbetween the filter 10 and the HVAC system ducting, and prevent any latermovement of the filter 10 relative to the HVAC system ducting.Alternatively, if the end portions of the filter have a greater diameterthan the ducting to which the filter 10 is to be connected, the shell 12may have a friction fit with the exterior surface of the ducting. Again,duct tape may be used to ensure a good fit, and to make certain that thefilter 10 does not move relative to the HVAC ducting.

Returning to the installation of the shell 12, once the seam is formed,then the shell 12, and correspondingly, the filter 10, is complete. Aswill be readily understood by one of ordinary skill in the art, thedisclosed filter configuration has far fewer parts than state-of-the-artfilters. The disclosed filter 10 has greater ease of manufacture, andproduces far less carbon dust in manufacture, because the granulatedactivated carbon is not repeatedly compacted, generating carbon dustwith each compaction. Further, any compaction takes place in theinterior of the mold, which contains the dust, and the mold may becleaned from time to time to prevent build up and escape of the dust.Thus, the filter 10 will also almost certainly produce less carbon dustin operation, as well.

In operation, the filter 10 may be placed in line with the air flow inan HVAC ducting system. Depending on the structure of the opposing endportions of the shell 12, the opposing end portions may be placed eitherin an interior of the HVAC ducting to which the filter 10 is beingconnected, or may be placed around an exterior of the HVAC ducting towhich the filter 10 is being connected. Duct tape may be used in eitherembodiment to seal the connection between the filter 10 and the HVACducting at each of the connection points on opposing ends of the filter10.

Once placed in the ducting system, the filter 10 will passively filterthe air flowing through the filter 10. Air in the HVAC ducting will flowuntil the air encounters the honeycomb carbon filter unit 14. A portionof the air molecules will contact the honeycomb carbon filter unit 14and the honeycomb carbon filter unit 14 will perform its filteringfunction. Other portions of the air will enter the honeycomb portion ofthe honeycomb carbon filter unit 14 without contacting the honeycombcarbon filter unit 14 at the first end.

Air molecules may flow through the honeycomb portion of the honeycombcarbon filter unit 14 until the air molecules contact the activatedcarbon of the honeycomb. There is some possibility that, due to theconfiguration of the honeycomb, some air molecules pass through thehoneycomb portion of the honeycomb carbon filter unit 14 withoutcontacting the activated carbon. Obviously, for those molecules that donot contact the honeycomb carbon filter unit 14, there is no filteringeffect. Thus, while embodiments without any other honeycomb carbonfilter unit 14 parts are less expensive, they may offer lesseffectiveness in operation.

One design choice to increase the number of air molecules that contactthe filter 10, and are thus filtered by the activated carbon, is toincrease the length of the honeycomb carbon filter unit. The longer thehoneycomb carbon filter unit is, the greater the probability that evenminor turbulence will cause air molecules to contact at least someportion of the honeycomb carbon filter unit. Additionally, the channelswithin the honeycomb may have smaller dimensions, which furtherincreases the likelihood that air molecules will contract the filter. Ofcourse, either of the design choices of lengthening the honeycomb carbonfilter unit or the smaller dimension of the channels may be usedindependently, or in combination.

Further, two of the embodiments discussed above offer additionalsolutions to, or, at least, substantial mitigation of, this potentialproblem. First, as discussed above, some embodiments have a piece ofcarbon material permeable to air stretched across the cross section ofthe honeycomb carbon filter unit 14. This piece of carbon materialserves not just to filter the air molecules passing through it, but alsoto disrupt the flow of the air molecules through the honeycomb portionof the honeycomb carbon filter unit 14. By disrupting the air flow, thelikelihood that air molecules pass through without contacting theactivated carbon, and therefore being filtered thereby, is greatlyreduced. At a minimum, air molecules will have to flow through thepermeable activated carbon material in the cross section, and thematerial performs some filtering by itself. The material placed acrossthe cross section of the honeycomb carbon filter unit 14 preventslaminar airflow, so the efficiency of air movement in the system isreduced. However, this is not a consideration for exhaust filtration.Additionally, the disruption of laminar flow is intentional, as it willcause air molecules to divert their path and contact the activatedcarbon material of the honeycomb. Further, the reorientation of theairflow discussed above more than compensates for any introducedinefficiency, and any of the embodiments of the disclosed filter 10 offmore efficient air flow. Ultimately, the disclosed air filter reducesthe fan power required by the system, which saves energy while producingsuperior filtration as compared to state-of-the-art filters.

Secondly, the end portions of the honeycomb carbon filter unit 14 may beshaped to provide some disruption effect. For example, the end portionsof the honeycomb carbon filter unit 14 may be shaped so as to create aVenturi effect for the incoming air. Because the air spirals with aVenturi effect, the air will be more likely to move into a verticaldivider 20 or a horizontal divider 22 or any part of the honeycomb crosssection. The first end portion and the second end portion may besymmetrical, so if the filter is reversed to make most efficient use ofthe activated carbon material, the disruption effect is the same.

The filter 10 will continue to provide filtration while there is stillnon-inundated activated carbon. State-of-the-art filters inherently havecertain flow paths which allow easier air flow than other potential airflow paths through the filter. Because the material in the honeycombcarbon filter unit 14 disclosed herein is much more uniform in structurethat the granulated material in state-of-the-art filters, virtually allflow paths are fungible. Because virtually all flow paths are fungible,air passes more evenly over the filtering material. Thus, there is moreefficient use of the filter material, and the disclosed filter providesbetter value for the money than state-of-the-art filters due to less ofthe activated carbon material being wasted. The material placed acrossthe cross section or the shaped end portions of the honeycomb carbonfilter unit 14 drive this more efficient usage by disrupting the laminarflow and randomizing it.

Moreover, because the filter is uniform, it may be reversed andreinstalled during its life cycle to promote even more efficient use. Itmay be that the portion of the honeycomb carbon filter unit 14 upstreamin the air flow may see more absorption of contaminants than the portionof the filter unit downstream. If such uneven wear is occurring, thesymmetry of the filter 10 will allow for correction. In order for theactivated carbon in the filter to wear evenly, the filter may beuninstalled, reversed so that the previously downstream portion is nowupstream, and reinstalled. The filter will wear more evenly andefficiently, and consequently, provide better value.

When the filter is no longer providing sufficient filtration due toabsorption of contaminants from the air, the entire filter may beremoved and replaced with a new filter. Even the process of removing andreplacing the filter is less costly than that of the state-of-the-artfilters because there is no need to access the interior of any ductingor other HVAC spaces. Rather, because the filter 10 is designed tooperate in line, the filter 10 is simply removed from the system, and anew one set in its place without having to access any interiors.

The filter disclosed herein offer further advantages overstate-of-the-art filters because of the disclosed filter's reduced size.Shipping costs are based on both size and weight. With both size andweight being reduced from the state-of-the-art filter in this abovedisclosed filter, the overall cost of the filter is lowered. With thestate-of-the-art filter transportation is a significant portion of thetotal cost. In addition to the design advantages already disclosedherein, the cost of transportation is also reduced.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein, including various ways of forming the structure whichcauses the air to flow in a predetermined pattern. Further, the variousfeatures of the embodiments disclosed herein can be used alone, or invarying combinations with each other and are not intended to be limitedto the specific combination described herein. Thus, the scope of theclaims is not to be limited by the illustrated embodiments.

What is claimed is:
 1. An air filter for filtering contaminants from aheating, ventilation, and cooling system, comprising: a first filterunit section of an activated carbon material, the first filter unitsection including one or more first exterior wall sections, a firstessentially planar wall section having a first essentially planarexterior surface extending between a first edge and a second edge of theone or more first exterior wall sections, and the first filter unitsection having a honeycomb structure cross section; a second filter unitsection of an activated carbon material, the second filter unit sectionincluding one or more second exterior wall sections, a secondessentially planar wall section having a second essentially planarexterior surface, and a honeycomb structure cross section, the secondessentially planar exterior surface of the second filter unit sectionbeing attached to the first essentially planar exterior surface of thefirst filter unit section so that the first filter unit section and thesecond filter unit section are mirrored and form a combined filter unithaving a first end and a second end; and a metallic shell around andadjacent to the one or more first exterior wall sections and the one ormore second exterior wall sections of the combined filter unit.
 2. Theair filter of claim 1, wherein the shell has one or more beads around acircumference of the shell.
 3. The air filter of claim 1, wherein theshell has a first bead and a second bead.
 4. The air filter of claim 3,wherein the first bead is adjacent to the first end of the combinedfilter unit, and the second bead is adjacent to the second end of thecombined filter unit.
 5. The air filter of claim 4, wherein an o-ring isplaced in each of the first bead and second bead.
 6. The air filter ofclaim 1, wherein the combined filter unit has a thermoset polymer on theone or more first exterior wall sections and the one or more secondexterior wall sections.
 7. The air filter of claim 1, wherein thecombined filter unit has a fiber compound on the one or more firstexterior wall sections and the one or more second exterior wallsections.
 8. The air filter of claim 1, wherein the combined filter unithas heat shrink tubing covering the one or more first exterior wallsections and the one or more second exterior wall sections.